Tetrapod Zoology

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In the previous articles we looked at the distribution and phylogenetic position of babirusas, and also at a bit of their behaviour, biology and morphology. While babirusas are famous for the bizarre upper canines that emerge from the dorsal surface of the snout in males, the function of these teeth remains uncertain. As we saw in the previous article, it’s been proposed that they function in display, in fighting, or in helping the animal to push its way through dense vegetation. The latter idea is least likely and is unsupported by observations. The fighting idea might seem logical and indeed MacKinnon (1981) proposed that a fighting male might hook one of his upper canines over one of the lower canines of his opponent, thereby both disarming the opponent and allowing unprotected access to his throat and face.

Incidentally, the picture above is one of Charles Tunnicliffe’s paintings from his Asian Wild Life Brooke Bond picture card set (for previous musings on this volume see my article on the most fantastic jerboa).

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The idea that the teeth function in fighting is not supported, however, by the fact that the teeth are brittle and easily broken. They’re also only shallowly rooted in their sockets (apparently), and are reportedly unsuited for withstanding large leverage forces (Macdonald 1993, Macdonald et al. 1993).

Furthermore, fighting male babirusas don’t use their upper canines at all, rather they stand bipedally and ‘box’ and prance round each other, each trying to either bite the opponent, or impale it on its lower canines [adjacent image from here: additional images - from the BBC series Life of Mammals - shown below]. Clayton (2003) reported that a combatant may be lifted clear of the ground during one of these fights, and that severe wounds may be inflicted on the neck of the lifted individual. It appears most likely that the upper canines function in display, though I don’t know of any studies testing this empirically.

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For previous babirusa articles see…

For other Tet Zoo articles on artiodactyls see…

Refs – -

Clayton, L. 2003. Tusk master. BBC Wildlife 21 (1), 52-57.

Macdonald, A. A. 1993. The babirusa (Babyrousa babyrussa). In Oliver, W. L. R. (ed) Pigs, Peccaries and Hippos Status Survey and Action Plan. IUCN/SSC Pigs and Peccaries Specialist Group & IUCN/SSC Hippos Specialist Group (Gland, Switzerland), pp. 161-171.

- ., Bowles, D., Bell, J. & Leus, K. 1993. Agonistic behaviour in captive Babirusa (Babyrousa babyrussa). Mammalian Biology 58, 18-30.

MacKinnon, J. 1981. The structure and function of the tusks of babirusa. Mammal Review 11, 37-40.

Comments

  1. #1 Owlmirror
    February 18, 2010

    [The teeth are] also only shallowly rooted in their sockets (apparently), and are reportedly unsuited for withstanding large leverage forces (Macdonald 1993, Macdonald et al. 1993).

    That shallow rooting makes me suspect even more that perhaps mechanical forces alone might be able to change the angle at which they grow, thus diverting the teeth into growing in the curves and angles seen in the skulls of the older ones.

    If there even exist any babirusa skulls that do have the upper canines impaling their skulls, perhaps these instances were the very rare results of them falling at just the right angle on top of them.

  2. #2 Darren Naish
    February 18, 2010

    I smell a paper. If only we knew someone who worked on babirusas…

  3. #3 Sordes
    February 18, 2010

    As I had to work a lot with orthodontics at the last time I think I can say some things about this issue. To change the direction of a growing tooth, you need continuous forces (they should be present at least 16 hours a day to cause actual change of the tooth direction and surrounding bone). A single “accident” would hardly change the tooth in its direction, but either break it or burst it out of the bone, or, if the accident was not that serious, have no long-time-effect. I suppose the curvature of the teeth is just a result of different speed in the prodction of the odontoblasts within the root. The dentogenesis is actually a really weird thing, and as far a tooth has erupted, there is no more change of the crown possible (of course abrasion is possible). Orthodontics also have nearly no effect on the growth of the root itself, but mainly on the surrounding bone. The application of pressure causes reduction of bone tissue, and the application of pulling forces causes bone production. This can cause sometimes extreme changes in the direction of the teeth, but it doesn´t change their actual shape.

  4. #4 Phil1078
    February 18, 2010

    I have been attacked by a 100kg male babirusa. I had an inch and a half tusk wound to the thigh. He lost two tusks, an upper and lower. He boxed with me, with the sharp hoof going into my shoulder. He also bit my had breaking tendons and ligaments. This all happened when a father was going after his mature son over the mother. I went in to real up the fight. The babirusa is normally very friendly and approachable except when feeding. Just thought I’d share this with everyone – babirusa fight people just like they fight each other. The upper tusk are rather brittle (I have the one he broke off on me). The lower tusk are stronger and are kept sharp by ribbing them on hard vertical structures. It was the bottom one that went into my thight when he got his head between my legs. Well that’s all, haha. Cheers!

  5. #5 Phil1078
    February 18, 2010

    Excuse my typos. I went in to break up a fight.

  6. #6 Tamara Henson
    February 18, 2010

    Wow – babirusas are the coolest animals.I like it when you update your 1st edition articles. Maybe next you can update your “are dogs really wolves?” post. A recent documentary I saw (Dingos, friend or foe? by IMP publishers) stated that recent DNA findings indicate that the dog/dingo clade predates the origin of the grey wolf. I would love to find out more about this.

  7. #7 Jerzy
    February 18, 2010

    Thanks!

    It reminds me that hippos and elephant seals also use lower tusks for stabbing and upper jaw for display.

  8. #8 Darren Naish
    February 19, 2010

    Tamara – thanks. That dog article is easiest the most controversial thing I’ve ever written, and I got in a lot of trouble about it. Not sure how I feel about it these days.

    Thanks for other messages too. Phil1078: I don’t suppose you have any photos you can share? I wonder if anyone else has ever been attacked by a babirusa?

  9. #9 retrieverman
    February 19, 2010

    I’m loving the babirusa series.

    One thing you haven’t mentioned yet is how many different species of babirusa exist and the biogeography, etc.

    I’m sure that’s coming.

  10. #10 Darren Naish
    February 19, 2010

    Yes – all this stuff is coming in the following parts.

  11. #11 Brian
    February 19, 2010

    The dingo/dog-split predating the origin of the modern radiation of the grey wolf is very interesting! Coincedentally, I’ve lately considered a scenario in which *C. familiaris* is a distinct species, yet part of the wolf radiation. With *C. lupus* sensu lato nowadays being considered a prime example of overzealous lumping it would seem perfectly possible for dogs to have originated as a rather more plesiomorphic ‘wolf’ species, comparable to *C. indica*,*C. lupaster* and *C. simiensis* but more derived.
    In this case, not the dog’s more hypocarnivorous habits and less extreme morphology compared to *C. lupus* are derived, but the grey wolf’s more extreme adaptations to hypercarnivory are.
    Is that feasible?

  12. #12 David Marjanović
    February 19, 2010

    *C. indica*

    C. indicus.

  13. #13 Owlmirror
    February 19, 2010

    To change the direction of a growing tooth, you need continuous forces (they should be present at least 16 hours a day to cause actual change of the tooth direction and surrounding bone).

    Hm.

    I wonder if when the tip of the tooth reaches the forehead, there is enough pressure transmitted back along the tooth?

    The application of pressure causes reduction of bone tissue, and the application of pulling forces causes bone production.

    So perhaps when the tooth tip grows enough to meet the forehead, this puts enough pressure on the cells on the anterior side of the root of the tooth, and pulls on the cells on the posterior side of the root of the tooth, resulting in differential growth that eventually moves the tooth tip away from the forehead?

    I’m not sure I’m getting that right. Perhaps it is completely unnecessary for there to be such feedback in order for there to be differential growth…

  14. #14 Allen Hazen
    February 19, 2010

    Tamara and Brian–
    I have not done ANYTHING rigorous here, but I have a subjective impression based on a bit of reading about canid phylogeny. Here’s my IMPRESSION: try to do a scatterplot of canine species, with hypocarnivorous to hypercarnivorous left to right and increasing body size bottom to top. My IMPRESSION is that the gray wolf would be way out in the upper right quadrant, and that things close to or derived from domestic dogs (“pariah dogs,” ferals, just plain mutts) would be a lot closer to the center. So A PRIORI I would think a scenario in which the ancestors of dogs (though closely related genealogically to the ancestors of wolves) branched off from wolves before wolves evolved their “classic” adaptations seems PLAUSIBLE.

    (For how much weight to put on my feelings, though, note that I am not a professional mammalogist, and reread the capitalized words above.)

    If he had the time and leisure and inclination to do it (no comment needed there), I’d love to see what Darren’s further thoughts on the matter would be.

  15. #15 Phil1078
    February 21, 2010

    Unfortunately, I do not have any pictures, haha. The doctors at the hospital asked for the same thing. Most of them were curious what got me.